you originally said
I have a target date field in my form , what I would like to record is the date when someone enters the target date for the first time only could you please advise the best way for me to do this
now you are saying
but I want to record that time from when it was opened until the target date was set
so by when it was opened, you don't mean from when the record was created, you mean you want the datetime someone completed the opened date and the datetime someone completed the target date, regardless of the values of those two fields
timestamp is just to show when the record was created - if that is the same as the time the opened date is populated you can use that,
plus Arnel's macro
Otherwise forget the timestamp column, you need two datetime columns and use a modification to Arnel's macro to update the two new fields
Or just use Arnel's macro and compare that to the opened date